Underfeed stoker



Oct. 5 1926. 1,601,717

L.. uuRwELl UNDERFEED STOKER Filed Feb. 2Q, 1924 2 Sheets-Sheet l FIN /fs4 E; I I f3( Y U E 58 43 F .4.

` l .0. B ur we ll wnmzsss: lNvENoR l BY WM ATTORN EY Oct. 5 1926. 1,601,717

L. D. BURWELL UNDERFEED STOKER Filed Feb. 20, '1924 2 Sheets-Sheet 2 F' .6. Fgf

l n. D. Burwe/l wnNEssEs; INVENTOR i BY ATTORNEY Patented Oct. 5, 192C.

UNITED STATES PATENT OFFICE.

LORING D. BURWELL, 0F MINNETONKA MILLS, MINNESOTA., ASSIGNOR T0 'WESTIING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF :PENNSYL- VANIA.

UNDERFEED STOKER.

Application filed February 20, 1924. Serial No. 694,004.

My invention relatesto underfeed Stoker furnaces, particularly to multiple retort stokers having a fuel supporting grate inclined fromthe front to the rear of the fur- 'nace and along which fuel is caused to travel with the aid of gravity, and it has for an object to provide means in a Stoker of the character designated which sha-ll assist in the maintenance of a uniformly rearwardly moving fuel bed of Substantially uniform permeability to air, to the end that a more even distribution of the fuel and air throughout the fuel bed, and hence a more complete and efficient combustion of the fuel, may be attained.

The objects of my invention may be secured by the employment of the apparatus illustrated in the accompanying drawing in which Fig. 1 is a fragmentary view in longitudinal Section through the center of a retort of an underfeedfurnace illustrating an embodiment of my invention; Fig. 2 is a fragmentary plan view of the lower portion of the Stoker illustrated in Fig. 1; Fig. 3 is a plan view on an enlarged scale of a tuyre construction shown in Fig. 1; Fig. 4t is a view in Section taken on line IV-IV of Fig. 3; Fig. 5 is a view in vertical section of one of the water supply reservoirs illustrated in Fig. 2; Fig. 6 is a fragmentary view in longitudinal section through the center of a retort showing a modified form of my invention applied to a different type of Stoker from that illustrated in Figs. 1 and 2; and Fig. 7 is a plan view of the retort bottom plate shown in Fig. 6.

It has been heretoforediiiicult in the op eration of multiple retort stokers to maintain a uniformly moving fuel bed due to the formation of clinkers adjacent the rear of the Stoker which offer material resistance.

to the rearward movement of the fue l bed. These clinker formations, further, give to the fuel bed characteristics which inhibit the even distribution of air through theV fuel bed with a consequent lack of uniformity in the rates of combustion at different portions of the fuel bed.

The underlying idea of the present application is based upon the fact that a more uniform rate of combustion throughout the fuel bed and a more complete and efficient combustion of the fuel can be Secured, and, indeed, more fuel per unit of grate surface can be effectively burned in an underfeed furnace, if a fuel bed of substantially uniform thickness and uniform air distributing capacity can be made to traverse the grate with equal rates of advancement from the entrance throat to the dum mechanism. Applicant perceived that this method of combustion had not heretofore been possible of" attainment because the almost completely burned fuel and clinker at the lower end of the furnace travels toward the discharge with a greater resistance to movement, due to the semi-plastic condition of the refuse and of the nearly burned fuel, than does the fuel at the upper portions of the grate. Consequently the oncoming fuel backs up behind the retarded fuel at. the rear of the furnace to form a heap large enough to exert Sufficient pressure on the lower parts of the fuel bed to overcome the added resistance to its rearward movement and to force it on to the discharge mechanism. Such heaps were heretofore considered to constitute the natural fuel bed contour.

Applicant conceived the idea of minimizing this heapedl fuel bed contour by lessening the resistance to the movement of the fuel at the rear of the underfeed grate, thus Securing the advantages of a fuel bed of uniform thickness through which air for supporting combustion could be more uniformly distributed. In other words, by making the resistance to movement of the fuel bed over the supporting metal of the grate substantially the same throughout the length of the fuel movements, the tendency to hea-ping of the fuel would be eliminated and it would be possible to maintain a fuel bed of substantially uniform thickness throughout the combustion area of the grate.

This result is accomplished in the present invention by adding to the air supply at the lower portion of the grate sufficient quantities of water to harden the surface of the semi-plastic refuse of the nearly consumed fuel so that it slides over the lower grate portions with the same facility that the fuel slides along the upper portions of thegrate tuyre banks 11, retorts 12, discharge mechanism 13, hopper 1d and plunger` 15, all of a conventional construction. The lower end of each of the retorts 12 is provided with tuyre plates 16, which plates cooperate with the lower ends of the tuyre banks 11 to support the rear portion of the fuel bed, that is, the ash and the nearly consumed fuel, prior to its delivery to the dump mechanism 13.

1n carrying out my invention in connection with the Stoker of the above described character, water is introduced with the air to the fuel bed at one or more zones in the rearward travel ot' the fuel. The number and disposition oit these water supply devices may be varied somewhat to meet diferent operating conditions arising by reason of the character of the ash content of the fuel. Where the fuel contains a large percentage of ash which is of low fusibility, the water-introducing devices should be increased in number and placed in higher positions. By way of illlustration of an embodiment of my invention which has proven satisfactory in operation for the usual low grade fuels, ll show two water distributing systems, one or supplying water to tuyres ot the tuyre banks 11 and the other for supplying water to the retort tuyres 16.

'lhe water distributing system associated with the tuyre banks 11 comprises a manifold 2O extending transversely beneath the tuyre and retort supports ot the Stoker and provided with risers or branch pipes 2l having their upper ends 22 laterally formed to discharge in a horizontal direction. As is more clearly shown in Figs. 1, 2 and 6, each of the horizontally extending nipples 22 is isposed within one of the air ports of the tuyre 11 and is preferably so located that the air beingdischarged through the port 25 surrounds the nipple 22. The nipple 22 should preferably terminate within the port 25 so that it will not be subjected to the heat of the burning fuel.

rlChe manifold 20 extends outwardly through the side wall 27 of the furnace where it is provided with a branch 28 having a valve 29 and leading into an elevated reservoir 30. The reservoir 30 should be located at such a level as to discharge water through the nipples 22 with a pressure head. Suitable means are provided for maintaining a uniformpressure head at the nipples 22 and also for varying the extent of this pressure head as changed combustion conditions may require. As shown in Fig. 5, an

inlet pipe 31, provided with a valve 32, supvplies water to the reservoir 30. A float 33 within the reservoir 30 has a depending guide stem 34 engaging a guide 35 and also a stem 36 extending upwardly through the top or cover 37 of the reservoir 30. A suitable link and lever system 38 ulcruxned at momia 39 upon a post 40 carried by the cover 37, connects the lloat 33 and the valve 32 in such a manner that the water admitted to the reservoir 30 is at all times sucient to maintain a predetermined level therein. The stem 36 is connected. to the lever mechanism 38 by means of an adjustable connection 1, which may be of any well-'known forni.

The water distributingr system for the retort tuyres comprises a manifold extending transversely beneath the tuyre supporting structure and provided with risers 51 which supply water to specially constructed tuyres 52. Each tuyre 52 is provided with a shallow basin 53 into which a riser 51 discharges water through an adjustable cap or nipple 54, hereinafter more fully described. An opening 56 for interlocking the tuyre 16 disposed above the special `'tuyre 52 is preferably formed with an upwardly extending boss 57, to

prevent the leakage of water from the basin 53. Fluted channels or corrugations 58 lead from thev basin 53 to the rear edge of the tuyre 52 and serve to direct both the air, which passes over the water in the basin 53 on its way from the` air chamber beneath the Stoker, and water from basin 53 to the fuel bed in the zone of the exposed surface 59 'of the tuyre 52.

As is shown in the drawing, any header 50 is capable of supplying water only to the tuyres 52 which are disposed in substantially the same horizontal plane, and since the water overflows from the basin 53 through the channels 58 it isL essential that some means for accurately proportioning the water to the several tuyres 52 be provided. This is accomplished in the construction illustrated in Fig. 4 by providing an externally and interiorly threaded cap 54 for the upper end of the pipe 51. rl`he tuyre 52 is provided with a threaded opening 6() into which the threaded cap 54 is turned. A hole 61 near the upper end of the cap 54%. provides an outlet for the Water rising within the header 5l. To regulate the relative amounts of water delivered through each of the several caps 54, it is only necessary to raise or lower the opening 61 by screwing the cap up or down in the opening of the tuyre 52. The header 50 is supplied with water from a reservoir 62, provided with means for controlling the pressure head in the header 50 in all respects similar to that described in connection with the reservoir 30. i

Having described an embodiment of my invention, the operation thereof is herein briefly set forth. Assuming that combustion has been initiated and that fuel is being supplied to the underfeed grate and 'is moving rearwardly toward the discharge mechanism in the conventional manner, the valves in the manifolds 2O and 50, respective- GFI lsmall full stream of water is thus caused to be discharged from the nipples 22 which being centrally disposed in an air discharging tuyre 25 permits the air blast to carry the water mixed more or less therewith to the fuel bed. If the nipples 22 have been disposed in a zone of travel of the fuel at which the partially burned fuel begins to assume a plastic condition, the action of the water upon the fuel is to make the clinker porous, thereby permitting free passage of air therethrough, and to harden or form a glass-like crust upon the surfaces of the fuel which come in contact with the water. The partially burned fuel is then in a condition to facilitate complete combustion of unburned portions and to slide easily over the metal 'surfaces of the fuel supporting elements.

The nipples 22 should be at the same level, since a full stream of water under a low head is distributed to each nipple and consequently any substantially irregularity in the level of the several nipples materially affects the amount of water discharged therefrom. It is also preferable to place the nipples 22 at such an angle that the water discharged therefrom not only affects the burning fuel immediately over the tuyre banks, but also the character of the fuel within the retorts.

`Where a number of tuyre plates form the bottom of the rear end of the retort, it. is also desirable to introduce waterinto the air discharged through one or more of these retort tuyres into the fuel bed. The tuyres selected for accomplishing this result are preferably nearer the rear end of the Stoker than those of the tuyre banks selected for the introduction of water with the air. In the retort tuyre disclosed in Figs. l to l, water is admitted with the air through the entire width of the tuyre and serves to affectnotonly the fuel passing over the retort tuyre, but also the fuel which is contiguous to the sides of the tuyres of the tuyre bank. This arrangement prevents adhesions of the hot fuel refuse not only upon the retort bottoni but at the angles between the retort tuyres and the side walls where adhesion of clinker masses readilytakesplace in the ordinary underfeed stoker. By a suitable dispositon of the water distributing devices above described, it is possible to maintain the fuel passing over the lower portions of the -Stoker grate in such condition that air for supporting combustion readily passes therethrough and no greater resistance 1s offered to its passage over the supporting surfaces of the grate than takes place in the upper portion of the grate. It consequently follows that the fuel moves rearwardly along the grate at asubstantially uniform speed and hence permits the fuel bed over the tuyre banks to maintain a substantially uniform thickness throughout the, entire course of the fuel travel through the furnace.

In Figs. G and 7, I show a modified form of my apparatus, applicable to an underfeed Stoker having dead plates at the rear of the bottom of the retorts instead of the tuyre plates of Figs. l to 4, the members 11', 20 21, 22', 25', and 50 corresponding to the members 11, 20, 2l, 22, Q5 and 50 respectively of Figs. l to t inclusive. In stokers of this type I employ specially constructed dead plates, preferably a rear dead plate 70, and a second dead plate 71. Each of the dead plates and 71 is provided at its forwardl end with a depression or basins T3 from whici extends rearwardly corrugations or channels 74. Tater is supplied to the basins T3 from the manifold 50 by means of risers T5. Means for regulating the relative flow of water to the basins T3, similar to that employed in connection with the retort tuyre 5:2, is employed. As shown in Fig. 6, the dead plates TO and 71 are cach provided with a depending tapped boss 7G beneath the basins 73. The risers 75 are threaded into the lower portions of the bosses 7G and nozzles 7S are threaded into the bottom of the basins, to communicate with the risers 75. The nozzles 78 have side outlet openings 79 to direct the water into the basins 73, which outlets may be raised or lowered to regulate the iiow of water therethrough by simoly screwing the nozzles 78 out of or into the bottoms of the basins.

The forward dead plates 71, as shown, have uprising flanges S0 in which are air emitting openings 8l, located to direct a blast of air into the fuel bed over dead plates. The air issuing from the openings Sl entrains some of the water from the basins T3 and in this way assists in distributing the moisture to the fuel.

The water discharged from the nozzles 22 and TS and the caps 5f is under a relatively low pressure head and consequently, where the water employed is not free from solid impurities, the water distributing members may become clogged and prevent a proper functioning of the Stoker. It is. therefore, desirable to provide in connection with the manifolds 20 and 50 some means for flushing the small distributing connections. In

some cases oftener. In flushing, the header 20 and vits distributing connections. for example, the valve 29 is closed and the valves4 91 and 95 are opened. The air needed for this purpose is preferably taken from the shop air line, in which a pressure in the neighborhood of 100 to 150 pounds is coininonly maintained. The high pressure air discharged from the nozzle 93 entraiis water from the pipe 90 and thus forces through the manifold 20, risers 21 and nozzles 22 an intimate mixture of air and water under high pressure. A short period of operation is sutiicient to remove all impurities from the water distributing system beine cleaned.

It has been found that a high pressure mixture of air-and water has greater cleansing capabilities than either air or water used alone. Satisfactory results have been obtained, however, where water alone has been used as a flushing agent, particularly where high pressure water is available for the yflushing action, and, consequently, I do not desire to limit the present invention to the'use of an air-water mixture as flushing agent.

vhile I have shown my invention in but two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed bythe prior art or as are specifically set forth in the appended claims.

lVhat I claim is V 1. In an underfeed Stoker having series of alternating retorts and tuyie banks, means for introducing water into a lower portion of each of the retorts for minimizing adhesions vof the refuse thereto.

2. In an underfeed Stoker having Vseries of alternating retorts and tuyre banks, means for introducing water through the tuyre banks into the lower portion of each of the retorts for minimizing adhesions of the refuse thereto.

3. In an underfeed stoker having series of alternating retorts and tuyre banks, means for delivering water to a lower portion of a tuyre bank for minimizing adhesions of the refuse thereto.

4. In an underfeed Stoker, the combination of a plurality of retorts, tuyre banks forming fuel supporting and air supplying means between the retorts, said tuyre banks being provided with channels for discharging air into said retorts, and means for introducing water in a lower portion of each of said retorts through one or more of said channels.

5. In an underfeed stoker, the combinal tion of a plurality of retorts, tuyre banks forming fuel supporting and air supplying means between the retorts, said tuyre banks being provided with channels for discharging air into said retorts, and means for introducing water in a lower portion of each of the retorts coii'comitantly with the air through one or more of said channels.

6. In an underfeed Stoker, the combination of a plurality of retorts, tuyre banks forming fuel supporting and air supplying means between the retorts, said tuyre banks being provided with channels so disposed as to discharge air both rearwardly and laterally, with the air discharged from one or more of said channels.

7. In an underfeed Stoker, the combination of a. plurality of retorts, tuyre banks forming fuel supporting and air supplying means between the retorts, said tuyre banks being provided with channels so disposed as to discharge air both rearwardly and laterally, a header disposed transversely to the retorts and extending therebeneath, and branch pipes leading from said header into some of said channels for the introduction of water into the air discharged therefrom.

8. In an underfeed Stoker,V the combination of a plurality of retorts, tuyre banks forming fuel supporting andair supplying means between the retorts, said tuyre banks.

being provided with channels so disposed as to discharge air both rearwardly and lat erally, pipes leading into some of said channels for the introduction of water into the air discharged therefrom, and means for supplying water to said pipes.

9. In an underfeed Stoker, the combination of a plurality of retorts, 'tuyre banks forming fuel supporting and air supplying means between the retorts, said tn vre banks being provided with channels so disposed as to discharge air both rearwardly and lat and means for introducing water',

erally, pipes lea ding into some of said chan nels for the introduction of water into the air discharged thereform, and automatic means for maintaining a uniform head of water in said pipes. y

10. In an underfeed stoker, the combination of a plurality of retorts, tuyre banks forming fuel supporting and air supplying means between the retorts, said tuyre banks .being provided with channels so disposed as to discharge air both rearwardly and laterally, pipes leading into some of said channels for the introduction of water into the air discharged therefrom, means for supplyingwater to said pipes, automatic means or maintaining a uniform head of water in said pipes, and means for adjusting the autoof alternating retorts and tuyres, means for introducing in llimited quantities of water under a relatively low pressure head into a lower portion of the fuel bed supported by said retorts and tuyres.

13. In an underfeed stoker having series of alternating retorts and tuyres, means for introducing a plurality of streams of water under relatively low pressure-into a lower zone of the f uel bed supported by said retorts and tuyres, saidzone extending substantially the width of the Stoker.

14. In a furnace grate, tuyere blocks for discharging air into the fuel bed including a plurality of tuyere blocks disposed in the same general horizontal plane, conduit means for supplying water under a low pressure head to the tuyres in said plane for facilitating the combustive action of the fuel, and means for forcing high pressure water through said conduit means for clearing foreign matter therefrom.

15. In afurnace grate, tuyere blocks fordischarging air into the fuel bed including a plurality of tuyere blocks disposed in the same general horizontal plane, conduit means for supplying water under a low pressurehead to the tuyres in said plane for facilitating the combustive action of the fuel, and means for passing mixed air and waterunder a high pressure head through said conduit means for clearing-foreign matter therefrom. l

In testimony` whereof, I have hereunto subscribed my name this leithpday of J anuy ary 1924. t

LORING D. BURWELL. 

